Is there a risk when adding a cap when it's not really neccessary?
Of course I'd like it to be even better so I guess I should now start investigating this VREF that I guess is how the arduino close the arduino 5V supply is to 5V. Is that correct? Is there a prefered method of doing this?
QuoteIs there a risk when adding a cap when it's not really neccessary?Yes.
The caps I'm talking about are the ones that are placed for each analog input.
Well maybe I'm just lucky but I'm actually very happy with the measurements which are within 0.01V from what my volt-meter measures. This has now been tested between 4-12V and between -5 to +25 degrees C. If this is consistent I don't need the results to be any better in this project.The measured voltage on my Arduino doesn't seem to change noticably when I add a volt-meter to the circuit and vice versa.It's all about the output impedance of whatever you are wiring to the analog input if the 10/11 megohm input impedance of your DMM will effect the reading or not. As the analogRead() command is optimized (and recommended) for reading a voltage source with an output impedance of 10K ohms or less, a DMM reading at the same time will have no effect noticeable.LeftyNow my problem is making the PCB which was harder then I imagined... a real puzzle.
2 x 10 Megohm resistors across it (R1 and R2), making a 1:1 divider
Quote2 x 10 Megohm resistors across it (R1 and R2), making a 1:1 dividerThat type of dividers are basically unusable for an avr's adc.